The covalent nature of the low-barrier N−H−N hydrogen bonds in the negative thermal expansion material H 3
[Co(CN) 6
] has been established by using a combination of X-ray and neutron diffraction electron density analysis and theoretical calculations. This finding explains why negative thermal expansion can occur in a material not commonly considered to be built from rigid linkers. The pertinent hydrogen atom is... (More)
The covalent nature of the low-barrier N−H−N hydrogen bonds in the negative thermal expansion material H 3
[Co(CN) 6
] has been established by using a combination of X-ray and neutron diffraction electron density analysis and theoretical calculations. This finding explains why negative thermal expansion can occur in a material not commonly considered to be built from rigid linkers. The pertinent hydrogen atom is located symmetrically between two nitrogen atoms in a double-well potential with hydrogen above the barrier for proton transfer, thus forming a low-barrier hydrogen bond. Hydrogen is covalently bonded to the two nitrogen atoms, which is the first experimentally confirmed covalent hydrogen bond in a network structure. Source function calculations established that the present N−H−N hydrogen bond follows the trends observed for negatively charge-assisted hydrogen bonds and low-barrier hydrogen bonds previously established for O−H−O hydrogen bonds. The bonding between the cobalt and cyanide ligands was found to be a typical donor–acceptor bond involving a high-field ligand and a transition metal in a low-spin configuration.
@article{00686d66-d789-40cc-b849-81dcaa508972,
abstract = {{<p><br>
The covalent nature of the low-barrier N−H−N hydrogen bonds in the negative thermal expansion material H <br>
<sub>3</sub><br>
[Co(CN) <br>
<sub>6</sub><br>
] has been established by using a combination of X-ray and neutron diffraction electron density analysis and theoretical calculations. This finding explains why negative thermal expansion can occur in a material not commonly considered to be built from rigid linkers. The pertinent hydrogen atom is located symmetrically between two nitrogen atoms in a double-well potential with hydrogen above the barrier for proton transfer, thus forming a low-barrier hydrogen bond. Hydrogen is covalently bonded to the two nitrogen atoms, which is the first experimentally confirmed covalent hydrogen bond in a network structure. Source function calculations established that the present N−H−N hydrogen bond follows the trends observed for negatively charge-assisted hydrogen bonds and low-barrier hydrogen bonds previously established for O−H−O hydrogen bonds. The bonding between the cobalt and cyanide ligands was found to be a typical donor–acceptor bond involving a high-field ligand and a transition metal in a low-spin configuration. <br>
</p>}},
author = {{Tolborg, Kasper and Jørgensen, Mads R.V. and Sist, Mattia and Mamakhel, Aref and Overgaard, Jacob and Iversen, Bo B.}},
issn = {{0947-6539}},
keywords = {{chemical bonding; electron density; hydrogen bonds; neutron diffraction; X-ray diffraction}},
language = {{eng}},
number = {{27}},
pages = {{6814--6822}},
publisher = {{Wiley-Blackwell}},
series = {{Chemistry - A European Journal}},
title = {{Low-Barrier Hydrogen Bonds in Negative Thermal Expansion Material H
<sub>3</sub>
[Co(CN)
<sub>6</sub>
]}},
url = {{http://dx.doi.org/10.1002/chem.201900358}},
doi = {{10.1002/chem.201900358}},
volume = {{25}},
year = {{2019}},
}
; Sist, Mattia
; Mamakhel, Aref
; Overgaard, Jacob
and Iversen, Bo B.
(2019)
In Chemistry - A European Journal
25(27).
p.6814-6822